Melt butter in pot or dutch oven over medium high heat. Add onion to dutch oven. Allow to cook, stirring only occasionally, until golden brown, about 10 minutes.
Add flour. Stir and allow to cook for several minutes until fragrant.
Stir in broth and milk. Allow to come to a boil and stir well until the gravy thickens. Add herbs, turkey, and frozen vegetables and allow to cook in gravy just until vegetables are no longer cold. Add salt and pepper, to taste.
Line a nine inch pie pan with your first crust. Add the turkey filling as full as you can (there might be leftover depending on the size of your dish).
Add the top crust and pinch the edges together. Cut a few slits in top crust to allow steam to escape.
Set pie dish on a baking sheet. Cook in lower third of preheated 425 degree F oven for 15 minutes, then reduce the heat to 375 degrees F and continue cooking until the crust is golden brown, about 30 more minutes.
You can use store bough pie crusts, but homemade pie crust is best.For the turkey, you can use: